Airmen upgrade GPS constellation

by Scott Prater
50th Space Wing Public Affairs

6/1/2010 - SCHRIEVER AIR FORCE BASE, Colo. -- Airmen from the 2nd Space Operations Squadron and from the 19th SOPS took control of the Air Force's newest GPS satellite following its launch into orbit May 28 from Cape Canaveral Air Force Station, Fla.

The GPS IIF SV-1 satellite represents a substantial upgrade for the GPS constellation. Thanks to improvements with the cesium-based atomic clocks used for timing, the satellite is expected to provide more accurate navigation signals than those of its predecessors.

The new IIF satellite also will broadcast two new signals: a jam resistant military code signal and a third civil signal known as the L5.

This latest addition is part of an ongoing modernization effort for the GPS constellation by Air Force officials.

"We're continuously replacing satellites in the constellation to ensure GPS remains the world's gold standard for position, timing and navigation," said Lt. Col. Mike Manor, the 2nd SOPS director of operations. "The GPS constellation is made up of 24 slots in space surrounding the earth where we place our satellites. This slot scheme and satellite placement ensures GPS users receive the most accurate navigation data at any time, at any place around the entire globe."

With the addition of the IIF SV-1, the GPS constellation now consists of 31 operational satellites. The idea is to keep newer satellites covering the primary slots. As the older satellites age, Air Force operators will move them out of the constellation and replace those primary slots with new vehicles.

"In a way, it's a constant transition as we continue to field newer and more capable vehicles," Colonel Manor said.

That constant transition into newer, more technologically advanced satellites has allowed the GPS wing, 2nd SOPS and 19th SOPS Airmen to exceed the required accuracy performance for GPS.

"We are exceeding the required sub-6 meters at 98 percent accuracy standard," Colonel Manor said. "We advertise that we are sub-3 meters on average, which is the most accurate GPS signal in the history of the program, so we're crushing the sub-6 meter requirement for our global users."

It's important to note the system's improving performance because military and civilian users worldwide have come to rely heavily on GPS.

Not since the invention of the radio has a free utility affected so many people on such a wide and varied scale. GPS service initially was designed and used for military purposes, but its civilian uses and popularity have brought the Air Force into an increasingly public arena.

GPS satellites provide combat capability for military applications, as well as ground vehicle and aircraft navigation aids. Civilians also use GPS as timing and navigation aids, plus they rely on GPS for power-grid management, banking, stock market transactions and cell-phone service.

Airmen in the GPS Operations Center receive 75 to 100 requests each week for various levels of support. Their primary mission is to support military users, providing them with information to take full advantage of the modernized utility of the GPS signal. "Any time a civil user of GPS reports a loss of GPS signal, we provide a current status of the GPS constellation and provide additional information to help them determine the cause of their outage," said 1st Lt. Caitlyn Diffley, a 2nd SOPS payload systems operator. "The vast majority of the time, I'd say 99 percent, the outage is related to some issue with the receiver unit, such as software glitches or installation issues."

Colonel Manor said in this most recent case, the issue involved a decryption problem with a specific vendor, which affected a specific military-use receiver.

The most recent launch of the new IIF satellite represents the first of 12 IIF satellites scheduled for launch in the next few years.

After a 3 to 4 month checkout of the new satellite, the vehicle will enter the operational constellation and begin broadcasting its navigation signal to users. The next IIF launch is anticipated for November.